s2ep2 Day of the Dragon

Basically the prototype for Steve McQueen's Nevada Smith.

Boy comes home to find parents murdered, home destroyed, vows to hunt down and kill Indians responsible. Wandering man who's expert with a gun mentors boy and helps him find peace.

Swap the Indians for ruthless bad guys and you have it. That, and the 'boy' is truly a boy in this episode, not a 40-ish man.